Field of the Invention
The present invention relates to an image forming apparatus that uses an electrophotographic system.
Description of the Related Art
In an image forming apparatus such as a copier, a printer, or a facsimile apparatus that uses an electrophotographic system or an electrostatic recording system, a toner image (a developer image) is formed by supplying toner (developer) to an electrostatic latent image that is formed on an image bearing member by scanning exposure. An image is then formed on a recording material by transferring the toner image onto the recording material and fixing the toner image thereon. In recent years, techniques for suppressing image lightening, scumming, and so on with the aim of stabilizing an output image by controlling the electrostatic latent image on the image bearing member have been proposed.
Japanese Patent Application Publication No. H5-66638, for example, proposes a technique of stabilizing a potential on an image bearing member surface by measuring the potential on the image bearing member surface and feeding the measured potential back to image formation control. Further, Japanese Patent Application Publication No. 2013-125097 and Japanese Patent Application Publication No. 2012-13381 propose a technique of calculating a surface potential by determining a discharge start voltage obtained when a bias is applied to the image bearing member, and feeding the calculated surface potential back to image formation control.
With the configuration described in Japanese Patent Application Publication No. H5-66638, however, the size of the image forming apparatus must be increased in order to measure the surface potential of the image bearing member. With the configuration described in Japanese Patent Application Publication Nos. 2013-125097 and 2012-13381, the surface potential of the image bearing member can be measured without increasing the size of the image forming apparatus. According to research undertaken by the inventors of the present application, however, the precision with which the surface potential is measured may decrease depending on the shape of the member used to measure the surface potential and the manner in which the image forming apparatus is used, and therefore demand remains for an improvement in precision.